An electrophotographic image forming apparatus employs a developing method in which the surface of an electrostatic latent image carrier (for example, a photoreceptor) is charged and the charged area is exposed according to image information to form an electrostatic latent image, and the electrostatic latent image is developed and visualized (developed).
Such a developing method includes single-component development which uses only a toner without using a carrier as a developer.
An example of a conventional developing device employing single-component development will be described with reference to FIG. 13 and FIG. 14. FIG. 13 is a schematic view showing a state of a toner before passing through a toner layer regulating blade in a conventional developing device, and FIG. 14 is a schematic view showing a state where a toner is further aggregated compared to the state of FIG. 13.
The developing device mainly consists of a developing roller 3 for developing a toner to a photoreceptor, a supply roller 2 for supplying and removing the toner to and from the developing roller 3, and a toner layer regulating blade 5k for adding a charge amount while regulating the toner supplied from the supply roller 2 to the developing roller 3 to a predetermined amount. The blade 5k is configured such that a rubber member 5q such as urethane is attached to a tip of a metal plate 5p. 
Here, for achieving high image quality, it is important to achieve an even toner layer on the developing roller 3 reaching a developing area.
A developing device described in Japanese Laid-Open Patent Publication No. 2000-187386 intends to stabilize an adhered amount and a charge amount of the toner layer on a developing roller after passing through a layer regulating blade by specifying an amount of intrusion of elastic rubber of the blade into the developing roller and a range of rubber hardness of the elastic rubber of the blade.
In the developing device described in Japanese Laid-Open Patent Publication No. 2000-187386, an amount of intrusion of the elastic rubber is reduced and the rubber hardness is decreased, so that a load on a toner is reduced to suppress deterioration of the toner.
In order to secure the charge amount of the toner, however, not less than a certain amount of intrusion of the elastic rubber and not less than certain rubber hardness are necessary, and it is difficult to realize securing of the charge amount and suppression of toner deterioration only by optimizing them.
The causes of the toner deterioration include that the blade presses the toner in a most proximate area of the blade and the developing roller and that the supply roller contacts with the developing roller and a load is applied to the toner when supplying the toner to the developing roller, whereas, in addition, the toner is deteriorated from the cause that the toner between the developing roller and the blade does not move and is gradually applied with pressure to aggregate in an upstream side of the most proximate area of the blade and the developing roller.
To describe the example of FIG. 13, although the toner that moved up on the developing roller 3 as shown by an arrow of solid line passes through the blade 5k to be regulated to a certain toner amount, a certain amount of the toner stagnates before passing through the blade. The stagnated portion is necessary for stabilizing the adhered amount of the toner after passing through the blade, but the toner gradually aggregates and stops moving because the toner is moved up continuously and is therefore subject to a compressing force. In addition, at this time, the toner that moved up collides with an aggregated toner Tc and a part of the toner is returned as shown by an arrow of dotted line, but the toner prominently aggregates due to this collision. Then, as shown in FIG. 14, a wide aggregation area Tz is formed as getting on a toner T which is below an averaged toner surface depicted by dotted straight line.
In this manner, when the toner aggregates in the area before passing through the blade, the toner capable of involving in the blade passing is reduced, and thereby the toner layer is not stabilized as well as toner deterioration due to the aggregation is advanced.